Skip to the content
 

The Vascular Biology Group

Platelets activate and adhere to the blood vessel wall
Mohammad al-Tamimi and Fiona (Tsz Man) Chang with Professor Michael Berndt and Associate Professor Jenny Rolland.

Laboratory Members

  • Mr Mohammad al-Tamimi
  • Dr Robert Andrews
  • Dr Jane Arthur
  • Mrs Cheryl Berndt
  • Professor Michael Berndt
  • Dr Elizabeth Gardiner
  • Ms Jing Jing
  • Mr David Leong
  • Dr Fi-Tjen Mu
  • Dr Yang Shen

Research  Background

Platelets are part of the cardiovascular system and normally circulate in blood in a quiescent form. In response to tissue injury, platelets become activated and form a thrombus (blood clot) to block further loss of blood and begin the process of tissue repair. Under certain conditions of inflammation or disease, platelets can aberrantly be activated to form a thrombus. This type of unrestricted thrombus formation can lead to blockage of cerebral vessels (stroke) or coronary vessels (heart attack).

Thrombosis precipitating heart disease and stroke is the leading cause of death in the Western world.

In thrombosis, platelet adhesion and aggregation are initiated by engagement of specific membrane receptors that lead to platelet activation and integrin-dependent aggregation. At high shear stress, platelet adhesion is mediated primarily by binding of the platelet membrane glycoprotein (GP) Ib-IX-V complex to its ligand, von Willebrand Factor (VWF), and binding of GPVI to collagen.

The binding of VWF to GPIb-IX-V is a critical event in initiating thrombosis. Distinct sites in the vWF A1 domain bind GPIb-IX-V, and leucine-rich repeats two through four of GPIb are involved in the binding of VWF. Signalling through GPIb-IX-V is dependent upon 14-3-3 zeta and the p85 subunit of PI 3-kinase, which bind to the alpha chain of GPIb. The cytosolic regulatory protein, calmodulin, also interacts directly with the cytoplasmic domains of both GPIb-IX-V and GPVI, associations that regulate the adhesive function and/or signal transduction mediated by these receptors. Activation of platelet signalling pathways leads to metalloproteinase-dependent shedding of platelet receptors, and is a key mechanism for regulation of platelet receptor levels and thus platelet function.

Our laboratory is currently pursuing the following projects

  • To identify the molecular determinants of VWF involved in recognition of platelet GPIb-IX-V, and how this interaction is regulated under shear conditions.
  • To examine the pathophysiological significance of receptor shedding from activated platelets.
  • To dissect the molecular interactions involved in 14-3-3 binding to PI3-kinase and to determine how 14-3-3 regulates the assemblage of GPIb-IX-V signalling complexes.
  • To characterize the functional significance of the receptor/14-3-3/PI3-kinase complex in transfected cells and animal models.
  • To analyze the function of calmodulin association with GPIb-IX-V and GPVI, in terms of ligand recognition, surface expression, cytoskeletal regulation or signalling.
  • To explore the adhesive interactions and signalling of platelet and leukocyte adhesion receptors involved in platelet-leukocyte-endothelial cell cross-talk.

Recent research papers from our group

Gardiner EE, al-Tamimi M, Mu FT, Karunakaran D, Thom JY, Moroi M, Andrews RK, Berndt MC, and Baker RI. Compromised ITAM-based platelet receptor function in a patient with immune thrombocytopenic purpura. J. Thromb. Haemostas. 2008; 5: 1530-1537.

Mu FT, Andrews RK, Arthur JF, Munday AD, Cranmer SL, Jackson SP, Stomski FC, Lopez AF, Berndt MC. A functional 14-3-3zeta-independent association of PI3-kinase with glycoprotein Ibalpha, the major ligand-binding subunit of the platelet glycoprotein Ib-IX-V complex. Blood 2008;  111: 4580-4587.

Gardiner EE, Karunakaran D, Arthur JF, Mu FT, Powell MS, Baker, RI, Hogarth PM, Kahn ML, Andrews RK and Berndt MC.Dual ITAM-mediated proteolytic pathways for irreversible inactivation of platelet receptors:De-ITAM-ising FcgRIIa. Blood 2008; 111: 165-174.

Wijeyewickrema LW, Gardiner EE, Moroi M, Berndt MC, Andrews RK.  Snake venom metallo-proteinases, crotarhagin and alborhagin, induce ectodomain shedding of the platelet collagen receptor, glycoprotein VI. Thromb. Haemost. 2007;  98: 1285-1290.

Arthur JF, Shen Y, Kahn ML, Berndt MC, Andrews RK, Gardiner EE. Ligand binding rapidly induces disulfide-dependent dimerization of glycoprotein VI on the platelet plasma membrane. J. Biol. Chem 2007; 282: 30434-30441.

Wijeyewickrema LW, Gardiner EE, Shen Y, Berndt MC, Andrews RK.Fractionation of snake venom metalloproteinases by metal ion affinity: a purified cobra metalloproteinase, Nk, from Naja kaouthia binds Ni2+-agarose. Toxicon. 2007; 50: 1064-1072.

Gardiner EE, Karunakaran D, Shen Y, Arthur JF, Andrews RK, Berndt MC. Controlled shedding of platelet glycoprotein (GP)VI and GPIb-IX-V by ADAM family metalloproteinases. J. Thromb. Haemostas. 2007; 5: 1530-1537.

Dunkley S, Arthur JF, Evans S, Gardiner EE, Shen Y, Andrews RK. A familial platelet function disorder associated with abnormal signaling through the glycoprotein VI pathway. Br. J. Haem. 2007; 137: 569-77.

Arthur JF, Shen Y, Mu FT, Leon C, Gachet C, Berndt MC, Andrews RK. Calmodulin interacts with the platelet ADP receptor P2Y1. Biochem J. 2006; 398: 339-343.

Shen Y, Cranmer SL, Aprico A, Whisstock JC, Jackson SP, Berndt MC, Andrews RK. Leucine-rich repeats 2-4 (Leu60-Glu128) of platelet glycoprotein Iba regulate shear-dependent cell adhesion to von Willebrand factor. J Biol Chem. 2006; 281: 26419-26423.

Arthur JF, Gardiner EE, Matzaris M, Taylor SG, Wijeyewickrema L, Ozaki Y, Kahn ML, Andrews RK, Berndt MC. Glycoprotein VI is associated with GPIb-IX-V on the membrane of resting and activated platelets. Thromb Haemost. 2005; 93: 716-723.

Gardiner EE, Arthur JF, Kahn ML, Berndt MC, Andrews RK. Regulation of platelet membrane levels of GPVI by a platelet-derived metalloproteinase. Blood. 2004; 104: 3611-3617.

Recent Reviews and Commentaries

Gardiner EE and Andrews RK The cut of the clot(h): snake venom fibrinogenases as therapeutic agents. J. Thromb. Haemost. 2008; 6: 1-3.

Arthur JF, Gardiner EE, Kenny D,Andrews RK, Berndt MC. Platelet receptor redox regulation Platelets 2008; 19: 1-8.

Berndt MC and Andrews RK. New direction for WE thrombin. Arterioscler. Thromb. Vasc. Biol. 2008; 28: 205-207.

Gardiner EE and Andrews RK. Platelet receptor proteolysis: GPVI and ADAM10. Chemistry Today 2007; 25: 58-61.

Arthur JF, Dunkley S, Andrews RK. Platelet glycoprotein VI-related clinical defects. Br. J. Haem. 2007; 139: 363-372.

Berndt MC, Karunakaran D, Gardiner EE,Andrews RK. Programmed autologous cleavage of platelet receptors. J. Thromb. Haemostas. 2007; 5: S1, 212-219.

Andrews RK, Karunakaran D, Gardiner EE, Berndt MC. Platelet Receptor Proteolysis: a Mechanism for Downregulating Platelet Reactivity. Arterioscler. Thromb. Vas. Biol 2007; 27: 1511-1520.

Gardiner EE, Arthur JF, Berndt MC, Andrews RK. Role of calmodulin in platelet receptor function. Curr Med Chem Cardiovasc Hematol Agents. 2005; 3: 283-287.

Yip J, Shen Y, Berndt MC, Andrews RK. Primary platelet adhesion receptors. IUBMB Life. 2005; 57: 103-108.

Andrews RK, Gardiner EE, Shen Y, Berndt MC. Platelet interactions in thrombosis. IUBMB Life. 2004; 56: 13-18

Andrews RK, Berndt MC. Platelet physiology and thrombosis. Thromb Res. 2004; 114: 447-453.

Andrews RK, Gardiner EE, Berndt MC. Snake venom toxins affecting platelet function. Methods Mol Biol. 2004; 273: 335-348.

Andrews RK, Gardiner EE, Shen Y, Berndt MC. Structure-activity relationships of snake toxins targeting platelet receptors, glycoprotein Ib-IX-V and glycoprotein VI. Curr Med Chem Cardiovasc Hematol Agents. 2003; 1: 143-149.

Other Selected Articles

Liu, J., M.E. Fitzgerald, M.C. Berndt, C.W. Jackson, and T.K. Gartner. 2006. Bruton tyrosine kinase is essential for botrocetin/VWF-induced signaling and GPIb-dependent thrombus formation in vivo. Blood 108:2596-2603.

Boylan, B., M.C. Berndt, M.L. Kahn, and P.J. Newman. 2006. Activation independent, antibody-mediated removal of GPVI from circulating human platelets: development of a novel NOD/SCID mouse model to evaluate the in vivo effectiveness of anti-human platelet agents. Blood 108:908-914..    

Baker, R.I., J. Eikelboom, E. Lofthouse, N. Staples, V. Afshar-Kharghan, J.A. Lopez, Y. Shen, M.C. Berndt, and G. Hankey. 2001. Platelet glycoprotein Ibalpha Kozak polymorphism is associated with an increased risk of ischemic stroke. Blood 98:36-40.

Munday, A.D., M.C. Berndt, and C.A. Mitchell. 2000. Phosphoinositide 3-kinase forms a complex with platelet membrane glycoprotein Ib-IX-V complex and 14-3-3z. Blood 96:577-584.

López, J.A., R.K. Andrews, V. Afshar-Kharghan, and M.C. Berndt. 1998. Bernard-Soulier syndrome. Blood 91:4397-4418.

Andrews, R.K., and M.C. Berndt. 1998. Adhesion-dependent signalling and the initiation of haemostasis and thrombosis. Histol Histopathol 13:837-844.

Stomski, F.C., Q. Sun, C.J. Bagley, J. Woodcock, G. Goodall, R.K. Andrews, M.C. Berndt, and A.F. Lopez. 1996. Human interleukin-3 (IL-3) induces disulfide-linked IL-3 receptor alpha- and beta-chain heterodimerization, which is required for receptor activation but not high-affinity binding. Mol Cell Biol 16:3035-3046.

De Luca, M., L.C. Dunlop, R.K. Andrews, J.V. Flannery, Jr., R. Ettling, D.A. Cumming, G.M. Veldman, and M.C. Berndt. 1995. A novel cobra venom metalloproteinase, mocarhagin, cleaves a 10-amino acid peptide from the mature N terminus of P-selectin glycoprotein ligand receptor, PSGL-1, and abolishes P-selectin binding. J Biol Chem 270:26734-26737.

Gamble, J.R., M.P. Skinner, M.C. Berndt, and M.A. Vadas. 1990. Prevention of activated neutrophil adhesion to endothelium by soluble adhesion protein GMP140. Science 249:414-417.

 

For more information on any of the work being carried out in this laboratory please contact Associate Professor Robert Andrews rob.andrews@med.monash.edu.au  Phone: 9903-0703